I. Technical Field
The present invention relates to an image blur correction apparatus (image stabilization device) mounted in, e.g., a lens body tube or a shutter unit of a digital camera and an image pickup unit having this image blur correction apparatus, and more particularly to a small and thin image blur correction apparatus applied to a camera mounted in a personal digital assistance such as a mobile phone and an image pickup unit having this image blur correction apparatus.
II. Description of the Related Art
As a conventional image blur correction apparatus (image stabilization device), there is known an image blur correction apparatus including a substantially rectangular base having an opening portion at the center, a first guide shaft provided on a front surface of the base, a first movable member supported to be reciprocable along the first guide shaft, a second guide shaft that is directed to a 90-degree direction with respect to the first guide shaft and provided on a front surface of the first movable member, a second movable member that is supported to be reciprocable along the second guide shaft and holds lenses, a first drive device that reciprocates the first movable member and the second movable member in a direction of the first guide shaft together, and a second drive device that reciprocates the second movable member in the direction of the second guide shaft, the apparatus adopting a voice coil motor including a coil and a magnet as each of the first drive device and the second drive device (see, e.g., Japanese Unexamimed Patent Application Publication No. 2007-296318).
However, this apparatus adopts a double configuration that the first movable member and the second movable member are aligned in an optical axis direction, and hence the apparatus increases in size in the optical axis direction. Further, although the second drive device drives the second movable member alone, the first drive device must drive not only the first movable member but also the second movable member and the second guide shaft together, and hence larger drive force must be generated as compared with a situation where the first movable member alone is driven, thereby resulting in an increase in size of the first drive device. Furthermore, since a drive load of the first drive device is different from a drive load of the second drive device, drive control for positioning the lenses within a plane vertical to the optical axis is not easy.
Furthermore, as another image blur correction apparatus (image stabilization device), there is known an image blur correction apparatus including a substantially rectangular base having an opening, four elastic support members (wires) that are implanted at four corners of a front surface of the base and extend in an optical axis direction, a movable member that is coupled with ends of the four elastic support members to hold lenses, a first magnet and a first yoke provided to the movable member, a second magnet and a second yoke provided to the movable member, and a substantially rectangular fixed frame that is fixed to another member different from the base and arranged in front of the movable member to hold a first coil and a second coil, the apparatus having a configuration that the first magnet, the first yoke, and the first coil constitute first a driving means, the second magnet, the second yoke, and the second coil constitute a second driving means, the first driving means drives the movable member in a first direction vertical to the optical axis, and the second driving means drives the movable member in a second direction vertical to the optical axis and the first direction (see, e.g., Japanese Unexamined Patent Application Publication No. 2008-64846and Japanese Unexamined Patent Application Publication No. 2007-233214).
However, in this apparatus, the size of the apparatus increases in the optical axis direction since the movable member is supported on the base by using the four elastic support members (the wires) that extend in the optical axis direction and the fixed frame holding the coil is supported by another member in front of the movable member. Further, the movable member (the lenses) may be possible to not only be moved in a plane direction vertical to the optical axis but also inclined with respect to the optical axis since the coupling portions of the four elastic support members are coupled in a rigid form rather than a link form, and desired return characteristics may be not obtained due to a variation per time in the elastic support members (the wires). Moreover, although the movable member is coupled with the base, since the fixed frame holding the coil is not integrally coupled, the image blur correction apparatus cannot be formed as a module, handling is inconvenient, the first magnet and the second magnet of the movable member and the first coil and the second coil of the fixed frame cannot be positioned with one member (e.g., the base) being determined as a reference, and hence an assembling operation of the apparatus is troublesome.
Additionally, as still another image blur correction apparatus (image stabilization device), there is known an image blur correction apparatus including a base, a movable member holding lenses, three balls and coil springs as a support mechanism that supports the movable member to be movable with respect to the base, a driving means (a driving magnet, a coil, and a yoke) for driving the movable member in a direction vertical to an optical axis, and a position detecting means (a magnet, a hall element) for detecting a position of the movable member (see, e.g., Japanese Patent No. 3969927).
In this apparatus, since the three rolling balls are interposed between the movable member and the base, thickness of the apparatus can be reduced in the optical axis direction, but the driving means must generate a driving force that can resist urging force of the coil springs because the coil springs exercise the urging force so that the movable member can be constantly supported in contact with the three balls and the urging force of the coil springs functions as a resisting force, i.e., a drive load when driving the movable member, an operation of latching the coil springs is troublesome, and an overall assembling operation is not easy.
Additionally, as yet another image blur correction apparatus (image stabilization device), there is known an image blur correction apparatus including a base, a movable member holding lenses, a first driving means (a magnet, a coil, a yoke) and a second driving means (a magnet, a coil, a yoke) for driving the movable member in two directions vertical to an optical axis, two assist springs configured to return (center) the movable member to a central position in a non-energized state (a pause state) that the coils are not energized, and others (see, e.g., Japanese Patent No. 3869926).
In this apparatus, since the assist springs are adopted as a returning means for returning the movable member to the central position, an arrangement space for the assist springs is required, an increase in size and others of the apparatus occurs, an operation of latching the assist springs is troublesome, and an overall assembling operation is not easy.